1. Field of the Invention
The present invention relates to a packing material, a tag, a certificate, paper money, and securities, each of which has a semiconductor device capable of wireless transmissions provided to a support medium (also referred to as a base material).
2. Related Art
A semiconductor device as typified by a wireless tag capable of transmitting and receiving data wirelessly such as identification information has been put to the practical use in various fields. The semiconductor device has been expected to expand a market as a new type information communication terminal. The wireless tag is also referred to as a RFID (Radio Frequency Identification) tag, or an IC tag. Most wireless tags that had been put to the practical use have an antenna and an integrated circuit (IC chip) formed by using a semiconductor substrate.
A wireless tag has advantages that there is no possibility that stored data is read by a physical method contrary to a magnetic card or a bar code, the data of which can be read wirelessly; and the stored data is difficult to be falsified. Further, contrary to a magnetic card or a bar code, the wireless tag has a merit that it is difficult to be forged since the manufacture of the wireless tag requires a comparative large productive facilities.
However, as the technique of counterfeit of the wireless tag is improved, it becomes difficult to prevent or detect counterfeit or deception by using simply a wireless tag.
In principle, a wireless tag can be formed to be smaller than a magnetic card, a bar code, or the like. Accordingly, it is expected to enlarge the range of usage of a wireless tag. It may be envisioned that a wireless tag is attached to a flexile material such as paper or plastic depending on its usage. However, a semiconductor substrate has a stronger mechanical strength than those of the foregoing materials. Therefore, if a wireless tag is provided to a packing material, a tag, a certificate, paper money, securities, and the like, each of which uses a flexible material as a support medium, there is possibility of breaking the wireless tag in use. Hence, it can be said that the wireless tag in this instance lacks in practicality.
The mechanical strength of a wireless tag can be improved to some extent by reducing its own area. However, in this instance, it becomes difficult to secure a circuit size or the gain of an antenna. Especially, it is unfavorable that the gain of an antenna is lowered since it leads to shorten a communications distance and restrict the usage of the wireless tag. Accordingly, the wireless tag area cannot be reduced blindly if importance is placed on the gain of an antenna. The limitations of improving a mechanical strength become arisen.
In case of an IC chip formed by using a semiconductor substrate, the semiconductor substrate serves as a conductor to shield an electric wave. Accordingly, there arises a problem that a signal tends to be attenuated depending on the direction of the signal being sent.